This invention relates to a semiconductor device, particularly to a semiconductor device equipped with a capacitor for storing information excellent in adhesiveness between a capacitor electrode film and an insulating film.
With recent miniaturization of semiconductor devices, there is a tendency to reduce the area of a capacitor for storing information. And it is likely for the value of capacity to decrease. The capacity C in the case of, e.g. a parallel plate electrode structure is determined by the formula: C=∈xc2x7S/d, wherein ∈ is a dielectric constant, S is an area of electrode, and d is a thickness of dielectric (a distance between electrodes). In order to secure the capacity without increasing the area of electrode S used in the capacitor for storing information, it is necessary to reduce the film thickness d of dielectric. At present, the film thickness of capacitor dielectric films (insulating films) is reduced to about 10 nm. In the case of integrated memories of 64 M bit or more, thinness of the capacitor dielectric films is becoming to a limit. For this reason, materials for capacitor dielectric films having higher dielectric constant ∈ are being developed now. For example, in the case of 64 to 256 M bit, the use of tantalum oxide (Ta2O5) is studied, and JP-A 9-186299 discloses the use of barium strontium titanate (BaxSrTisOt: BST), etc. for 1 G bid DRAM. Further, as non-volatile memories, JP-A 10-189881 discloses the use of lead zirconate titanate (PbxZryTisOt: PZT), etc.
It is known that these oxide films such as BST and PZT do not exhibit good properties unless subjected to high temperature treatment, such as as high as about 600xc2x0 C. or higher. Thus, as the capacitor. electrode materials contacting with the oxide film such as BST, PZT, etc., it is necessary to use a material which is hardly oxidized at high temperatures. This is because when the capacitor electrode is made of a material easily oxidized, oxidation reaction takes place at a contacts interface between the electrode and. the oxide film at high temperatures to deteriorate properties of the oxide film. From the above-mentioned background, there have been studied as hardly oxidized capacitor electrode materials noble metals such as rhodium (Rh), ruthenium (Ru), iridium (Ir), osmium (Os), platinum (Pt), etc., and electroconductive oxides such as ruthenium oxide (RuxOy) and iridium oxide (IrxOy), etc.
It is known that oxide films such as BST and PZT do not exhibit good properties unless subjected to high temperature treatment as mentioned above. And in order to use for DRAM having 1 G bit or more, it becomes to know that sufficient properties are not exhibited unless subjected to high temperature treatment in an oxygen atmosphere. Thus, in the production of DRAM having 1 G bit or more, it is necessary to conduct a high temperature treatment at about 600xc2x0 C. or higher in an oxygen atmosphere. But, noble metals such as ruthenium which is studied as the electrode material have poor adhesion to silicon oxide (SiO2) used as an insulating film, and show a problem of adhesive fracture when subjected to high temperature treatment particularly in oxygen atmosphere.
It is an object of the present invention to provide a semiconductor device improved in adhesiveness between capacitor electrodes formed by using as a principal material a noble metal such as ruthenium, platinum, or the like, or an electroconductive oxide such as ruthenium oxide, iridium oxide, or the like and an insulating film containing silicon. Another object of the present invention is to provide a semiconductor device having higher reliability. A further object of the present invention is to provide a semiconductor device having enhanced yield in the production thereof. The present invention still further provides a process for producing these semiconductor devices.